The present invention relates to an ear plug usable for prevention of noise, acoustic instruments such as hearing aids, and so on.
FIG. 1 shows the prior art ear plug wherein a sponge-like sleeve member 2 is fixed on an exterior of a core member 1 in a body. An external enlarged portion la of the core member 1 has a shallow vent 3 formed therethrough to loose a pressure difference between an interior of the external auditory canal and the external atmosphere when the ear plug is inserted into the external auditory canal. The core member 1 is formed as a part of a hearing aid 12.
It is required that the ear plug is superior in prevention of noise of high frequency when inserted into the external auditory canal. However, if the degree of prevention of noise is improved at that time, there occurs a pressure difference between the external atmosphere and an inside of the external auditory canal, accompanied by problems such as feeling of oppression with clogging of the ear. The pressure difference can be avoided by manufacturing the core member 1 in a straight form, however, sound generated from the hearing aid 12 having an external portion 1a of the core member 1 is easy to leak outward due to the short length of the vent in the core member 1. This causes so-called howling to remarkably decrease the performance of the ear plug.
Consequently, an object of the present invention is to lengthen a communicating passage or vent to an effective degree for remarkably decreasing the pressure difference between the inside of the external auditory canal and the external atmosphere as well as preventing leakage of sound causing so-called howling.
In order to realize this object, the present invention provides an ear plug to be interted into the external auditory canal, having a compressible sleeve member and a core member attached therein, the improvement in which plural projections or a single projection are formed intermittently or continuously on an exterior of the core member, and vent is formed through or along the projection to make the external auditory canal communicate with the external atmosphere when inserted into the external auditory canal.
According to the present invention, the projections are formed on the exterior of the core member and the vent is defined through or along the projection to make the external auditory canal communicate with the external atmosphere, so as to lengthen a communicating passage or vent to an effective degree for remarkably decreasing only the pressure difference between an inside of the external auditory canal and the external atmosphere as well as preventing leakage of sound causing so-called howling.
In the present invention, it is preferable that an innermost vent is formed through an innermost projection of the intermittently formed projections or through an inner end portion of the core member to open into the external auditory canal, other vents are formed through other respective projections, and an outermost vent is formed through an outer end portion of the core member to open into the external atmosphere.
In this case, the vents are preferably formed at different positions of adjacent projections, and each of the projections can be ring-shaped.
It is also preferable that a continuous vent or groove is formed along the continuously formed projection to make an outermost vent communicate with the external auditory canal, and an outermost vent is formed through an outer end portion of the core member to open into the external atmosphere.
In this case, an additional vent is preferably formed through an inner end potion of the core member, and the continuously formed projection can be spiral-shaped.
It is further preferable that the sleeve member is composed of a sponge-like material such as polyurethane and the core member is composed of a flexible material such as polyethylene, so as to be deformed to meet the shape of the external auditory canal, and that a penetrating lumen is formed through an inside of the core member from one end to another end.
A hearing aid can has the core member in one body.